While small melanocytic nevi with congenital features can be routinely encountered in general pathology, pediatric pathology, and dermatopathology practices, large and giant congenital melanocytic nevi (CMN), proliferative nodules, and cutaneous melanomas arising in CMN are exceptionally rare and can pose significant diagnostic challenges for morphologists with limited exposure to them. Added to this challenge is the potential for proliferative nodules and melanomas arising in CMN to demonstrate overlapping clinical, histological, and immunohistochemical findings despite their stark differences in prognosis and management. A reliable distinction between these lesions may be difficult even for expert pathologists without the use of ancillary molecular testing in ambiguous cases. This chapter will review the clinical, histological, immunohistochemical, and molecular features of CMN, proliferative nodules, and melanomas arising in CMN to help pathologists become more aware of and accurately recognize these uncommon melanocytic lesions.